Calculating Required Powder for Coating Mud rotors

[demionkrishan]

Gents,
I am so weak in mathematics, So far i used to understand the amount of required powder by daily monitoring each similar job and taken average consumption. I feel my DE rate is low and wasting powders a lot therefore i am having very less margin, which is very difficult to run the bussiness as well.

Example: I have a mud rotor length 6.8M and 6.75 Ø
Let say i am using Woka-3652 - cost per Kg is 60 USD
Density of powder 5g /cm3
if i want to calculate required powder & Cost per 100 microns

Surface area X density X Thickness X cost of Powder is enough? or is there any otherway

Surface area - 2 x pi x r x h = 2x3.14x (6.75/2)x25.4) x 6800 mm
therefore = 3660m 2

Density - 5g /cm3

Thickness - 0.01

Required powder = 36600 x 5 x 0.01 + 15 % over spray / wastage
therefore = 2104 g with 100% efficiency
if my DE is 40% then = 3kg per 100 Microns


Gordon / vadim / DJ and all expertise please advise and guide me ..

[AdamT]

Gents,
I am so weak in mathematics, So far i used to understand the amount of required powder by daily monitoring each similar job and taken average consumption. I feel my DE rate is low and wasting powders a lot therefore i am having very less margin, which is very difficult to run the bussiness as well.

Example: I have a mud rotor length 6.8M and 6.75 Ø
Let say i am using Woka-3652 - cost per Kg is 60 USD
Density of powder 5g /cm3
if i want to calculate required powder & Cost per 100 microns

Surface area X density X Thickness X cost of Powder is enough? or is there any otherway

Surface area - 2 x pi x r x h = 2x3.14x (6.75/2)x25.4) x 6800 mm
therefore = 3660m 2

Density - 5g /cm3

Thickness - 0.01

Required powder = 36600 x 5 x 0.01 + 15 % over spray / wastage
therefore = 2104 g with 100% efficiency
if my DE is 40% then = 3kg per 100 Microns


Gordon / vadim / DJ and all expertise please advise and guide me ..

I see a two flaws in your logic. First off, you can't use the powder's apparent density because this value includes all the voids between the powder particles. If you were to melt a kilo of powder into a perfectly filled block, the volume it would occupy would be much smaller. You must calculate yourself the material's density based on it's chemical composition. In this case, I calculate that Woka 3652 should have a density around 13.9 g/cm3. That means it would actually take 5.85kg of powder at 100% efficiency.

You also made a mistake when calculating the powder it would take with 40% DE. At 40% DE, it means that in order to deposit the required 5.85kg, you would have to spray 14.625 kg of powder. The way you calculated it was equivalent to 70% DE and I have no idea how you got there.

[Vadim Verlotski]

Hi Kirshan,

I agree with AdanT that you have made a mistake in layer density (WC86Co10Cr4 has a density of 13.9-14.0 g/cm3). But you have also calculated the surface area of your mud rotor incorrectly.
A cylinder with a diameter of 6.75 inches (171.45 mm) and a length of 6800 mm has a surface area of 3.66 m2, but a mud rotor is not a cylinder, its surface area is significantly larger. I do not know how to calculate the surface of the rotor from its diameter (there is certainly an online calculator for it), but I would have roughly taken factor 2 larger surface area compared to cylinder, so about 7 m2.

Weigh of 7 square meters coating with 100 microns thickness and density of 14 g/cm3 is: 70000x0.01x14 = 9800 grams, approx. 10 kg. At 40% order efficiency, it means for you: 10 / 0.4 = 25 kg of powder per 100 μm layer.

Unfortunately, the order efficiency of mud rotors coating is significantly lower in comparison with cylinder coating (spraying angles are less than 90°). I estimate that your order efficiency will not be more than 20%. Ultimately, this means that for 100 microns layer thickness about 50 kg of powder will be necessary.

Regards
Vadim

[Stephen Booth]

this is a very interesting discussion, something the the job shop faces regularly: How to seriously and accurately record, and hopefully improve the efficiency of the process, and each individual jobs.

There is obviously a huge difference between 50 kg @ 60$ or 3000$ per part (plus time and and labour) and the 15 kgs....

Great discussion

if looking for a belt grinding attachment, please check this.... http://www.bexxonglobal.com/polishing-of...otors.html

[demionkrishan]

AdamT & Vadim,
Thanks for your valuable comments here. I feel it is huge subject, where we cannot find the real value.

Density=Mass/Volume
WOKA composition is 86Wc10Co4Cr
Tungsten Density- 15.63g/Cm3
Cobalt - 8.9g/Cm3
Chromium - 7.19g/cm3
therefor - 14.61 g/Cm3 it's fine

But i have still doubt about the surface area, as you mentioned it is helical solid profile so, how do you calculate as 7m2??

Do we need to consider here about RPM & robot traverse to calculate the consumption of powder?


Thanks
D>K

Gordon,
Please do input your comments as well.

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Hi Vadim,

Unfortunately, the order efficiency of mud rotors coating is significantly lower in comparison with cylinder coating (spraying angles are less than 90°). I estimate that your order efficiency will not be more than 20%. Ultimately, this means that for 100 microns layer thickness about 50 kg of powder will be necessary.

Currently for 6.75" Ø rotor we are consuming about 35-38 Kg 3652 powder to achieve 500 Microns layer. Still i feel, it is low, as per METCO, DE will be 40-60% I have done few trails to know our current DE, it is below 45% . I do not understand how to achieve at least 50% of DE from my current setup and parameters? , aslo how METCo has given 20% gap between min and max......

[sprayloud]

I would make a model of the rotor in 3D program (solidworks or other).
Then i would make another model with dimensional changes with coating in mind.
Solidworks can give you volume of the body, so the difference will be the volume of your coating. You just have to multiply it by density to get the mass of powder. I would say thats the most accurate method of calculating. Of course in real life your mass will be higher because of the overspray.
If you spray rotors of the same diameter with the same gun, you can calculate "real density" including overspray for future jobs.